The overall objective of the research in this laboraotry is to elucidate the mode of pathogenesis of Pseudomonas aeruginosa. In the next year, we will concentrate our efforts on the characterization of its phospholipase, particularly on the attachment of cell wall or cell membrane material to this enzyme, its effect on the function and stability of the enzyme and its effect on the role that is played by the enzyme in the pathogenesis. We continue our effort that we started recently to characterize the siderophores, or the iron chelating agents, of this species. There are more than one type of these agents that we call pyochelins and their chemical natures as well as their biological functions will be a major topic of our research. The ability of P. aeruginosa to produce pyochelins enable the organism to grow in serums and it is one of the major virulence factor of the organism. The pyochelins in some cases block the attachment of pyocins to the cell surface and therefore, they protect the organisms from the lethal effect of the latter. Interactions of these substances and their roles in the ecology as well as the pathogenesis of the organism will be studied. We are still continuing our efforts to establish an international standard for serotyping of P. aeruginosa based on the heat stable somatic antigens.